Mobile communications terminals, such as cellular phones or other audio devices, typically include a speaker on the terminal housing for emitting sound to the user's ear, and may also include a wired or wireless earpiece, such as on a headset, for emitting sound to the user's ear without requiring the user to hold the terminal next to the ear. The use of the speaker on the terminal housing may be referred to as a “handset mode” of operation, and the use of a separate headset may be referred to as a “headset mode.”
Headsets may take various forms, including headphones, which are speakers that are held adjacent an outer portion of the ear, and earphones or earbuds, which are positioned inside the ear canal. Various types of headsets are referred to herein as “earpieces.”
The sound characteristics as heard by the user's ear may change with the position and application of force to the user's ear, which may cause varying degrees of acoustic leakage. The leak tolerance of the particular headset may be improved by acoustical and/or mechanical designs. However, such designs may require relatively powerful and large transducers with associated disadvantages in terms of size, weight, and/or power consumption for the mobile terminal. Moreover, the leakage results in a variation in frequency response such that some frequencies are affected differently than other frequencies. For example, when the acoustic leakage is relatively large, it is generally more difficult for the user to hear low frequencies. Therefore, increasing the volume of the speaker does not adequately address problems with acoustic leakage.